Biomass is organic matter with a plant or animal origin. It ranges from plants such miscanthus which are specifically grown for the purpose, to human sewage. Biomass can produce energy directly, for example burning wood to produce heat. As carbon dioxide was used as the tree grew, the burning of it is deemed to be carbon neutral, it is a shame about the particulates which are released.
Alternatively, the biomass can undergo chemical or electrochemical conversion. The most common method is anaerobic digestion, where the biomass is attacked by bacteria in the absence of oxygen to produce a mixture of carbon dioxide and methane. This can be burnt to generate heat and electricity, and is referred to as bioenergy.
The bioenergy is carbon neutral, because carbon dioxide was sequestered by the biomass in the first place. If the carbon dioxide released is then captured and stored, the process becomes carbon negative. This is known as BECCS, BioEnergy Carbon Capture and Storage. Look at link for more information on CCS.
An example is Omnagen’s innovative self-powered CO2 converter; a device which converts carbon dioxide, methane and air into useful chemicals, without the need for external energy. This is how the device works.
Carbon dioxide is a very stable molecule, it will react with some minerals to form stable carbonates, but other reactions require energy. Photosynthesis, for example, uses energy from the sun to convert CO2 and water into glucose and oxygen.
CO2 is only a problem if it is in the earth’s atmosphere. The greenhouse effect is explained here.
Carbon Capture and Storage (CCS) involves capturing CO2 from the air, or exhaust gases, liquifying it, and then burying it. This is expensive, but it will allow fossil fuels to be used without releasing carbon dioxide into the atmosphere. More details about CCS.